Integrated process to produce 2,3,3,3-tetrafluoropropene

ABSTRACT

The invention relates to a separation process whereby 2-chloro-3,3,3-trifluoropropene (1233xf) is separated from a mixture containing other fluorinated organics and high boiling materials such as dimers using azeotropes of HF formed by adding appropriate amounts to the mixture which facilitate separation by, e.g. distillation.

FIELD OF THE INVENTION

The present invention relates to a process for preparing fluorinatedorganic compounds, more particularly to a process for preparingfluorinated olefins, and even more particularly to a process forproducing 2,3,3,3-tetrafluoropropene (HFO-1234yf).

BACKGROUND OF THE INVENTION

Certain hydrofluoroolefins (HFOs), such as tetrafluoropropenes(including 2,3,3,3-tetrafluoropropene (HFO-1234yf)), are now known to beeffective refrigerants, heat transfer media, propellants, foamingagents, blowing agents, gaseous dielectrics, sterilant carriers,polymerization media, particulate removal fluids, carrier fluids,buffing abrasive agents, displacement drying agents and power cycleworking fluids. Unlike most chlorofluorocarbons (CFCs) andhydrochlorofluorocarbons (HCFCs), most HFOs pose no threat to the ozonelayer. HFO-1234yf has also been shown to be a low global warmingcompound with low toxicity and, hence, can meet increasingly stringentrequirements for refrigerants in mobile air conditioning. Accordingly,compositions containing HFO-1234yf is a leader among the materials beingdeveloped for use in many of the aforementioned applications.

A manufacturing process for HFO-1234yf, as e.g. disclosed in U.S. Pat.No. 8,058,486, uses 1,1,2,3-tetrachloropropene (HCO-1230xa) as startingraw material. The process consists of the following three steps: (1)HCO-1230xa+HF-->2-chloro-3,3,3-trifluoropropene (HCFO-1233xf)+HCl in avapor phase reactor charged with a solid fluorination catalyst, (2)HCFO-1233xf+HF-->2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb) in aliquid phase reactor charged with a liquid hydrofluorination catalyst,and (3) HCFC-244bb-->HFO-1234yf in a vapor phase reactor.

As also disclosed in U.S. Pat. No. 8,058,486, subsequent to Step (1)above, the effluent stream exiting the vapor phase reactor is fed to afirst recycle column. The lighter components, including HCl,HCFO-1233xf, HCFC-244bb, HFC-245cb, and small amounts of HF, areisolated as a top light stream, and are fed to next unit operation as acrude first intermediate stream. The majority of the un-reacted HF andheavy intermediates are isolated as a bottom heavy stream, and are fedback to the vapor phase reactor of Step (1). Nevertheless, high boilerssuch as 1230xa dimers, e.g. C₆H₃F₆Cl, C₆H₃F₇Cl₂, C₆F₆Cl₂, C₆H₈Cl₂,C₆F₅Cl₃, C₆H₃F₂Cl₅, and the like, are also included in this bottom heavystream that is sent to the vapor phase reactor, where such materials cancause the deactivation of catalyst.

As disclosed in U.S. Provisional Patent Application No. 61/604,629,filed Feb. 29, 2012, in an improved integrated process, a phaseseparator is used to receive the said bottom heavy stream so as toconcentrate these non-recyclable high boilers. While the 1233xfcontained in the HF phase of the separator is recycled back to the Step(1) reactor together with HF, substantial amounts of 1233xf and otherrecyclable byproducts such as 1232xf, 243 isomers, etc. are stillpresent in the organic phase, together with non-recyclable high boilers.Due to the presence of high boilers, it is difficult to further isolaterecyclable species using conventional distillation method. Hence, thereis a need for means by which 1233xf and other recyclable byproducts canbe efficiently recovered.

SUMMARY OF THE INVENTION

The present invention relates, in part, to one or more process steps forimproving the reaction efficiency used for the production of HFOs, suchas 2,3,3,3-tetrafluoropropene (1234yf).

In one aspect, the present invention relates to a process for preparing2-chloro-3,3,3-trifluoropropene by providing a starting compositionincluding at least one compound of formula I, II, and/or III

CX₂═CCl—CH₂X  (I)

CX₃—CCl═CH₂  (II)

CX₃—CHCl—CH₂X  (III)

wherein X is independently selected from F, Cl, Br, and I, provided thatat least one X is not fluorine. Such a starting composition is contactedwith a fluorinating agent, such as HF, to produce a final compositionincluding 2-chloro-3,3,3-trifluoropropene (1233xf), HCl, unreacted HF,optional unreacted starting compound(s), and one or more by-products.The by-products may include, without limitation, one or a combination oftrichlorofluoropropene (1231) isomers, 2,3-dichloro-3,3-difluoropropene(1232xf), 2-chloro-1,1,1,2-tetrafluoropropane (244bb),1,1,1,2,2-pentafluoropropane (245cb), dichlorotrifluoropropane (243)isomers, trichlorodifluoropropane (242) isomers, and dimer(s) such asC₆H₃F₆Cl, C₆H₃F₇Cl₂, C₆F₆Cl₂, C₆H₈Cl₂, C₆F₅Cl₃, C₆H₃F₂Cl₅, and the like.In certain aspects, at least one of the compounds is recyclable back tothe contacting step.

This final composition is then processed to separate desired productsand recyclables from the remainder of the final composition. In oneaspect, 1233xf and HCl are first separated by feeding the compositioninto a recycle or distillation column. From such a column, the lightercomponents, such as 1233xf, 244bb (if any), 245cb (if any), HCl, and aportion of unreacted HF are isolated in a first or top stream, and theremaining components, such as unreacted HF, optional unreacted startingcompounds, one or more by-products, and residual 1233xf are recovered ina second or bottom stream. From this first or top stream, 1233xf ispurified using standard distillation methods, such as those providedherein. It, the 1233xf, is then forwarded to the second step of thereaction (discussed below) to produce 244bb and, ultimately, 1234yf.

The bottom stream of the recycle or distillation column is then furtherprocessed to isolate recyclable compounds from Step (I) of the reactionaforesaid. Unreacted HF, for example, is substantially separated byphase separation. More specifically, the second or bottom stream fromthe recycle column is provided to a phase separator where unreacted HFseparates into a first layer (or HF-rich layer). In certain embodiments,this first layer also includes, as a residual portion, certain of theorganics such as, but not limited to, 1233xf, 1232xf, and 243. Theremaining organics (e.g. optional unreacted starting compound, residual1233xf, and one or more by-products, which may include 1231, 1232xf,243, 242, and various dimers, are separated into a second layer (ororganic-rich layer). The HF-rich first layer is then extracted,optionally purified, and recycled.

The organic-rich layer of the phase separator may be similarly extractedand further processed to recover the unreacted starting material (ifany), residual 1233xf, and other recyclable by-products such as 1231,1232xf, 243, 242, and the like for recycling. In one aspect, theextracted organic-rich stream is sent to a distillation column forprocessing. In a preferred embodiment, to better recover the unreactedstarting material (if any), 1233xf and other recyclable by-products, HFis added to the mixture during distillation in an amount sufficient toform various binary and/or ternary azeotropic or azeotrope-likecompositions with hydrogen fluoride, and thereafter the azeotropic orazeotrope-like compositions are separated from high boiling pointnon-recyclable by-products such as dimers. Non-limiting examples ofazeotropic or azeotrope-like compositions include 1230xa/HF, 1233xf/HF,1232xf/HF, 244bb/HF, 243db/HF, 1233xf/244bb/HF, etc.

The instant invention relates to the finding that the addition of HF tothe extracted organic-rich stream from the phase separator provides foreasier recovery of 1233xf and other recyclable by-products. The economyof the process is therefore improved. Additional embodiments andadvantages to the present invention will be readily apparent to one ofskill in the art, based on the disclosure provided herein.

In one embodiment, the invention relates to a separation process whichcomprises:

providing a first composition comprising i)2-chloro-3,3,3-trifluoropropene (1233xf), ii) one or more organicsselected from the group consisting of trichlorofluoropropene (1231)isomers, 2,3-dichloro-3,3-difluoropropene (1232xf),2-chloro-1,1,1,2-tetrafluoropropane (244bb),1,1,1,2,2-pentafluoropropane (245cb), dichlorotrifluoropropane (243)isomers, trichlorodifluorpropane (242) isomers, and optionally iii) oneor more dimers selected from the group consisting of C₆H₃F₆Cl,C₆H₃F₇Cl₂, C₆F₆Cl₂, C₆H₈Cl₂, C₆F₅Cl₃, C₆H₃F₂Cl₅;adding HF to said first composition in an amount effective to form asecond composition comprising HF-azeotropes of 1233xf and of at leastone of the organics;separating at least a portion of the HF-azeotropes from the secondcomposition.

In one embodiment, the invention relates a process to prepare2-chloro-3,3,3-trifluoropropene (1233xf) comprising providing a startingcomposition comprising at least one starting compound of formula I, IIand/or formula III

CX₂═CCl—CH₂X  (I)

CX₃—CCl═CH₂  (II)

CX₃—CHCl—CH₂X  (III)

wherein X is independently selected from F, Cl, Br, and I, provided thatat least one X is not fluorine;

-   -   (a) contacting said starting composition with a fluorinating        agent under conditions effective to produce a first composition        comprising 1233xf, unreacted fluorinating agent, HCl, optionally        unreacted starting compound, and one or more organics selected        from the group consisting of trichlorofluoropropene (1231)        isomers, 2,3-dichloro-3,3-difluoropropene (1232xf),        2-chloro-1,1,1,2-tetrafluoropropane (244bb),        1,1,1,2,2-pentafluoropropane (245cb),        dichlorotrifluoropropane (243) isomers,        trichlorodifluorpropane (242) isomers, and optionally one or        more dimers selected from the group consisting of C₆H₃F₆Cl,        C₆H₃F₇Cl₂, C₆F₆Cl₂, C₆H₈Cl₂, C₆F₅Cl₃, C₆H₃F₂Cl₅, and        combinations thereof;    -   (b) separating, from the first composition, a second composition        comprised of an amount of 1233xf and substantially all of said        organics and optionally dimers;    -   (c) adding HF to the second composition in an amount effective        to form a third composition comprising HF-azeotropes of 1233xf        and at least one of the organics, said second composition        further comprising the optional dimers;    -   (d) separating the HF-azeotropes from the third composition; and    -   (e) recovering 1233xf from the HF-azeotopes separated in step        (d).

The 1233xf that is separated using the invention can be recycled andotherwise used in processes to make materials such as 244bb and 1234yf.

DETAILED DESCRIPTION OF THE INVENTION

The foregoing general description and summary and the following detaileddescription are exemplary only and are not restrictive of the inventionas defined in the appended claims. Other features and benefits of any ofthe embodiments herein will be apparent from the present disclosure. Theentire contents of U.S. Pat. No. 8,084,653 and US Published PatentApplication 2009/0240090 are incorporated herein by reference.

According to one embodiment, the present invention relates to amanufacturing process for making 2,3,3,3-tetrafluoroprop-1-ene using astarting material according to any one or combination of Formulas I, II,and/or III:

CX₂═CCl—CH₂X  (Formula I)

CX₃—CCl═CH₂  (Formula II)

CX₃—CHCl—CH₂X  (Formula III)

wherein X is independently selected from F, Cl, Br, and I, provided thatat least one X is not fluorine. In certain embodiments, the compound(s)of Formula I, II and/or III contains at least one chlorine, a majorityof the Xs as chlorine, or all Xs as chlorine. In certain embodiments,the compound(s) of Formula I includes 1,1,2,3-tetrachloropropene(1230xa). In certain embodiments, the compound(s) of Formula II includes2,3,3,3-tetrachloropropene (1230xf). In further embodiments, thecompound(s) of Formula III include 1,1,1,2,3-pentachloropropane (240db).

The method generally includes at least three reaction steps. In Step(1), a starting composition including compounds of Formula I, II, and/orIII (e.g. 1,1,2,3-tetrachloropropene, 2,3,3,3-tetrachloropropene, and/or1,1,1,2,3-pentachloropropane) is reacted with anhydrous HF in a firstvapor phase reactor (fluorination reactor) under conditions effective toproduce a mixture of 2-chloro-3,3,3-trifluoropropene (12334 and HCl. Incertain embodiments, the reaction occurs in the vapor phase in thepresence of a vapor phase catalyst, such as, but not limited to, afluorinated chromium oxide. The catalyst may (or may not) have to beactivated with anhydrous hydrogen fluoride HF (hydrogen fluoride gas)before use depending on the state of the catalyst.

While fluorinated chromium oxides are disclosed as the vapor phasecatalyst, the present invention is not limited to this embodiment. Anyfluorination catalysts known in the art may be used in this process.Suitable catalysts include, but are not limited to chromium, aluminum,cobalt, manganese, nickel and iron oxides, hydroxides, halides,oxyhalides, inorganic salts thereof and their mixtures and any one ofwhich may be optionally fluorinated.

Combinations of catalysts suitable for the present inventionnonexclusively include Cr₂O₃, FeCl₃/C, Cr₂O₃/Al₂O₃, Cr₂O₃/AlF₃,Cr₂O₃/carbon, CoCl₂/Cr₂O₃/Al₂O₃, NiCl₂/Cr₂O₃/Al₂O₃, COCl₂/AlF₃,NiCl₂/AlF₃ and mixtures thereof. Chromium oxide/aluminum oxide catalystsare described in U.S. Pat. No. 5,155,082 which is incorporated herein byreference. Chromium (III) oxides such as crystalline chromium oxide oramorphous chromium oxide are preferred with amorphous chromium oxidebeing most preferred. Chromium oxide (Cr₂O₃) is a commercially availablematerial which may be purchased in a variety of particle sizes.Fluorination catalysts having a purity of at least 98% are preferred.The fluorination catalyst is present in an excess but in at least anamount sufficient to drive the reaction.

This Step (1) of the reaction may be conducted in any reactor suitablefor a vapor phase fluorination reaction. In certain embodiments, thereactor is constructed from materials which are resistant to thecorrosive effects of hydrogen fluoride and catalyst such as Hastalloy,Nickel, Incoloy, Inconel, Monel and fluoropolymer linings. If desired,inert gases such as nitrogen or argon may be employed in the reactorduring operation.

When the compound of Formula I is 1230xa, the mol ratio of HF to 1230xain Step (1) of the reaction is 1:1 to 50:1, from about 10:1 to about50:1, or from about 10:1 to about 20:1. The reaction between HF and1230xa is carried out at a temperature from about 200° C. to about 600°C., in certain embodiments, about 200° C. to about 400° C., or about200° C. to about 300° C. The reaction pressure is about of about 0 psigto about 500 psig, in certain embodiments from about 20 psig to about200 psig, or about 50 to about 100 psig.

Similarly, when the compound of Formula II is 1230xf, the mol ratio ofHF to 1230xf in step 1 of the reaction is 1:1 to 50:1, from about 10:1to about 50:1, or from about 10:1 to about 20:1. The reaction between HFand 1230xf is carried out at a temperature from about 200° C. to about600° C., in certain embodiments, about 200° C. to about 400° C., orabout 200° C. to about 300° C. The reaction pressure is about of about 0psig to about 500 psig, in certain embodiments from about 20 psig toabout 200 psig, or about 50 to about 100 psig.

Similarly, when the compound of Formula III is 240db, the mol ratio ofHF to 240db in step 1 of the reaction is 1:1 to 50:1, from about 10:1 toabout 50:1, or from about 10:1 to about 20:1. The reaction between HFand 240db is carried out at a temperature from about 200° C. to about600° C., in certain embodiments, about 200° C. to about 400° C., orabout 200° C. to about 300° C. The reaction pressure is about of about 0psig to about 500 psig, in certain embodiments from about 20 psig toabout 200 psig, or about 50 to about 100 psig.

The fluorination reaction may be carried out to attain a single- ormulti-pass conversion of at least 1% or higher, 5% or higher, 10% orhigher or about 20% or higher. In certain preferred embodiments of thepresent invention, the starting reagent is converted to 1233xf in asingle pass, wherein the reaction conditions achieve a conversion amountgreater than 75%, greater than 85%, greater than 95% or greater than99%. To this end, the resulting effluent includes small or trace amountsof unreacted starting material or may be substantially free of suchcompounds.

The effluent from the fluorination reaction step, Step (I), includingany intermediate effluents that may be present in multi-stage reactorarrangements, are processed to achieve desired degrees of separationand/or other processing. For example, in embodiments in which thereactor effluent includes 1233xf, the effluent will generally alsoinclude HCl, unreacted HF, and trace amounts, if any, of unreactedstarting component (e.g. 1230xa, 1230xf and/or 240db). The effluent mayalso include one or more by-product organics such as underfluorinatedand/or overfluorinated intermediates. Non-limiting examples ofunderfluorinated intermediates include trichlorofluoropropene (1231)isomers and 2,3-dichloro-3,3-difluoropropene (1232xf), and non-limitingexamples of overfluorinated intermediates include2-chloro-1,1,1,2-tetrafluoropropane (244bb) and1,1,1,2,2-pentafluoropropane (245cb). Other by-product organics may alsoinclude, but are not limited to, dichlorotrifluoropropane (243) isomers,and trichlorodifluoropropane (242) isomers, and dimers derived from oneor more of the starting compounds. By way of non-limiting example,dimers derived from 1230xa include, but are not limited to, C₆H₃F₆Cl,C₆H₃F₇Cl₂, C₆F₆Cl₂, C₆H₈Cl₂, C₆F₅Cl₃, C₆H₃F₂Cl₅, and the like.

The effluent from Step (1) may be processed in one or more steps toisolate the 1233xf, as well as certain unreacted components and/orbyproducts that are useful as recyclables. In one embodiment, startingreagent is provided to a drier and then to the reactor along with HF.The effluent stream exiting the vapor phase reactor is fed to a coolerand then to a first recycle column, such as a distillation column. Thelighter components of the effluent are isolated from the top of thefirst recycle column and cooled and include one or more of HCl, 1233xf,244bb (if any), 245cb (if any) and a portion of unreacted HF. Theremaining compounds are collected at the bottom stream of the column andinclude a bulk of the unreacted HF, trace amounts of unreacted startingcomponent (if any), residual 1233xf and one or more of the by-productorganics discussed herein. When referring to the bottom stream of thecolumn, a “residual” amount of 1233xf refers to less than about 30 wt %,less than about 20%, less than about 15%, or less than about 10% of thetotal weight of the components in the bottom stream.

Each of the top stream and bottom stream are then independentlyprocessed. The top stream, for example, is first fed into an HCl columnfor HCl removal. High purity HCl is isolated from the top of the columnand fed to an HCl recovery system. By way of non-limiting example, insuch a recovery system HCl from the top stream may be absorbed inde-ionized water as concentrated HCl, which, optionally, can berecovered for later sale. The remaining components, including 1233xf,244bb (if any), 245cb (if any), and HF, exit the bottom of the HClcolumn and are further processed. In certain embodiments, this bottomstream is then provided to an HF recovery system to recover HF. The1233xf/HF stream is fed to a sulfuric acid extractor or a phaseseparator for removal of HF from this mixture, i.e. the HF is eitherdissolved in sulfuric acid or phase separated from the organic mixture.With the former, HF is desorbed from the sulfuric acid/HF mixture byheating and distillation and recycled back to the reactor. In the casewhere a phase separator is used, HF is phase-separated using standardmethods, such as those discussed below, and recycled back to thereactor. The organic either from the overhead of the sulfuric acidextractor or from the bottom layer of the phase separator is fed to thehydrofluorination reactor of Step (2), discussed below.

Components within the bottom stream of the first recycle column areseparated, in certain embodiments, by phase separation. Morespecifically, the mixture is provided to a cooler and then to a phaseseparator where unreacted HF separates into an HF-rich first or toplayer and an organic-rich bottom or second layer. In one practice,separation is such that substantially all of the HF from the mixture isin the top layer, and substantially all of the organics and/or dimersfrom the mixture are in the bottom layer. “Substantially all” as usedherein means more than half. Thus in the present context, “substantiallyall” means that more than half of the HF in the mixture is separatedsuch that it is in top layer, and respectively, that more than half ofthe organics and/or dimers in the mixture are separated such that theyare in the bottom layer. More than half includes those percentages fromover 50% (e.g. over 50% of the HF from the mixture is separated into thetop layer of the phase separation process) up to and including 100% andall intermediate values. The phrases “HF-rich” and “organic-rich” havethe same quantitative meaning as “substantially all.” Any pressure whichmaintains the mixture substantially in the liquid phase may be employed.To this end, the pressure and temperature of the mixture may be adjustedsuch that the mixture remains substantially in the liquid phase. Incertain embodiments, the HF-rich layer also includes, as a residualportion, certain of the organics such as, but not limited to 1233xf,1232xf and 243 isomers. The remaining organics not provided in the firstlayer (particularly unreacted starting compound(s) (if any), residual1233xf, 242 isomers, 243 isomers and dimers) separate into theorganic-rich second or bottom layer. (When referring to the top layer, a“residual portion” of organics refers to less than about 50 wt %, lessthan about 40%, less than about 30%, less than about 20%, or less thanabout 10% of the total weight of the components in the top layer.) Phaseseparation may be performed at any combination of temperature andpressure such that two distinct liquid phases are formed in the phaseseparator. Phase separation may be carried out between about −30° C. to60° C., preferably between about 0° C. and 40° C. and more preferablybetween about 10° C. and 30° C.

The HF rich layer is then isolated, such as by HF phase pump, optionallypurified, and recycled back to the reactor via vaporizer. In oneembodiment, the HF-rich layer is distilled to remove any moisturebuildup or is isolated by single stage flash distillation. In anotherembodiment, before the recycle of HF-rich stream moisture (if any) isremoved by injecting a chemical reagent such as COCl₂ (or SOCl₂) intosaid stream, which reacts with moisture to form CO₂ (or SO₂) and HCl. Ineven further embodiments, the HF-rich layer may be purified to removethe residual organics or may be recycled with the organics.

The organic-rich layer is also isolated, such as by organic phase pump,then further processed to separate and purify the unreacted startingreactants (if any) and recyclable intermediates. In certain embodiments,the organic-rich layer is provided to a high boiler purge system, whereunreacted starting reagents (if any), residual 1233xf, 1231 isomers,1232xf, 243 isomers, 242 isomers, etc. are recovered and undesirableby-products, particularly dimers and other impurities, are removed. Whenreferring to the organic-rich layer, a “residual” amount of HF refers toless than about 15 wt %, less than about 10%, less than about 5%, orless that about 3% of the total weight of the components in the bottomlayer. Organics in this regard are, without limitation, those selectedfrom the group consisting of trichlorofluoropropene (1231) isomers,2,3-dichloro-3,3-difluoropropene (1232xf),2-chloro-1,1,1,2-tetrafluoropropane (244bb),1,1,1,2,2-pentafluoropropane (245cb), dichlorotrifluoropropane (243)isomers, trichlorodifluorpropane (242) isomers, and the like.

The high boiler purge system may be a distillation system operated inbatch or continuous mode, preferably batch for operational reasons.Another option is to use a flash or series of flashes. In either case(distillation or flash), the more volatile components are recovered andrecycled while the heavier components are removed from the system. Inone non-limiting embodiment, the organic-rich layer is isolated, such asby organic phase pump, and is provided to a batch distillation columnfor separation. The lighter components (e.g. unreacted startingcompounds including HF, 1231 isomers, 1232xf, residual 1233xf, 242isomers, and 243 isomers) are isolated from top stream(s).Non-condensable compounds (if any) are optionally purged and the lightercompounds are collected as a series of distillation cuts where compoundsare separated in order of volatility. It is noted that any number ofdistillation cuts may be provided to separate the valuable or recyclablematerials, e.g. unreacted starting compounds, 1231 isomers, 1232xf,1233xf, 243 isomers, 242 isomers, etc. Once isolated, unreacted startingcompounds, 1233xf, 1231 isomers, 1232xf, 243 isomers, 242 isomers may berecycled to the reactor of the first step. In doing so, the unreactedstarting components (if any) and the recyclable intermediates areconverted to the desired composition 1233xf and/or its precursors. Theheavy compounds (e.g. dimers, etc.) are isolated from the bottom stream.Dimers in this regard include, without limitation, materials such thoseselected from the group consisting of C₆H₃F₆Cl, C₆H₃F₇Cl₂, C₆F₆Cl₂,C₆H₈Cl₂, C₆F₅Cl₃, C₆H₃F₂Cl₅ and the like.

In a preferred embodiment of the present invention, to better recoverthe unreacted starting material (if any), 1233xf and other recyclableby-products such as 1231 isomers, 1232xf, 243 isomers, 242 isomers, HFis added to the mixture during distillation in an amount effective toform HF-azeotropes of 1233xf and at least one of the organics, e.g. inan amount effective to form various binary and/or ternary azeotropic orazeotrope-like compositions of the organics with the hydrogen fluoride;thereafter the azeotropic or azeotrope-like compositions are separatedfrom high boiling point non-recyclable by-products such as dimersincluding C₆H₃F₆CI, C₆H₃F₇Cl₂, C₆F₆Cl₂, C₆H₈Cl₂, C₆F₅Cl₃, C₆H₃F₂Cl₅, andthe like. Non-limiting examples of azeotropic or azeotrope-likecompositions include 1230xa/HF, 1233xf/HF, 1232xf/HF, 244bb/HF,243db/HF, 1233xf/244bb/HF, etc.

The concentration of HF in the resultant mixture after HF addition canvary in a wide range from 5 to 95 wt %, preferably from 20 to 80 wt %,and more preferably from 30 to 70 wt %.

In one practice of the invention, the addition of HF to the extractedorganic-rich stream from the phase separator allows for easier recoveryof 1233xf and other recyclable by-products. The economy of the processis therefore improved.

Removal of the high boiling point by-products and impurities isadvantageous because such compounds cause catalyst deactivation ifrecycled. During phase separation, as set forth above, such compoundstend to concentrate in organic layer. Accordingly, post-isolation, theorganic layer can also be purified in accordance with the foregoing toremove such compounds and isolate only those compounds that arerecyclable. Removal of the high boiling point compounds results inimproved catalyst life and minimal purge streams.

In Step (2) of the aforementioned process for forming2,3,3,3-tetrafluoroprop-1-ene, the purified 1233xf intermediate streamis converted to 2-chloro-1,1,1,2-tetrafluoropropane (244bb). In oneembodiment, this step may be performed in the liquid phase in a liquidphase reactor, which may be TFE or PFA-lined. Such a process may beperformed in a temperature range of about 70-120° C. and about 50-120psig.

Any liquid phase fluorination catalyst may be used in the invention. Anon-exhaustive list include Lewis acids, transition metal halides,transition metal oxides, Group IVb metal halides, a Group Vb metalhalides, or combinations thereof. Non-exclusive examples of liquid phasefluorination catalysts are an antimony halide, a tin halide, a tantalumhalide, a titanium halide, a niobium halide, and molybdenum halide, aniron halide, a fluorinated chrome halide, a fluorinated chrome oxide orcombinations thereof. Specific non-exclusive examples of liquid phasefluorination catalysts are SbCl₅, SbCl₃, SbF₅, SnCl₄, TaCl₅, TiCl₄,NbCl₅, MoCl₆, FeCl₃, a fluorinated species of SbCl₅, a fluorinatedspecies of SbCl₃, a fluorinated species of SnCl₄, a fluorinated speciesof TaCl₅, a fluorinated species of TiCl₄, a fluorinated species ofNbCl₅, a fluorinated species of MoCl₆, a fluorinated species of FeCl₃,or combinations thereof. Antimony pentachloride is most preferred.

These catalysts can be readily regenerated by any means known in the artif they become deactivated. One suitable method of regenerating thecatalyst involves flowing a stream of chlorine through the catalyst. Forexample, from about 0.002 to about 0.2 lb per hour of chlorine can beadded to the liquid phase reaction for every pound of liquid phasefluorination catalyst. This may be done, for example, for from about 1to about 2 hours or continuously at a temperature of from about 65° C.to about 100° C.

This Step (2) of the reaction whereby 244bb product is formed is notnecessarily limited to a liquid phase reaction and may also be performedusing a vapor phase reaction or a combination of liquid and vaporphases, such as that disclosed in U.S. Published Patent Application No.20070197842, the contents of which are incorporated herein by reference.To this end, the 1233xf containing feed stream is preheated to atemperature of from about 50° C. to about 400° C., and is contacted witha catalyst and fluorinating agent. Catalysts may include standard vaporphase agents used for such a reaction and fluorinating agents mayinclude those generally known in the art, such as, but not limited to,hydrogen fluoride.

The effluent from the hydrofluorination reaction step, Step (2), whichconsists mainly of 244bb and HF (plus small amounts of unreacted 1233xf,overfluorinated by-product 245cb, HCl, and Cl₂), is processed to achievedesired degrees of separation and/or other processing. For example, theproduct stream is fed to a lights removal column where a streamconsisting of mainly 245cb, HCl, and Cl₂ exits the top of the column andis sent to a thermal-oxidizer (T-OX) for destruction. In one practice,the lights removal column bottom stream consisting of mainly 244bb andHF (plus a small amount of unreacted 1233xf) is fed into a phaseseparator for HF recovery. The HF rich top layer is recycled back to theStep (2) reactor. The organic rich bottom layer containing mainly 244bb(plus small amounts of HF and 1233xf) is sent forward, together with anHF stream, to a distillation column for separation. The concentration ofHF in the resulting mixture, in an embodiment, is between about 0.01% byweight to about 20% by weight; in another embodiment, the concentrationHF is between about 0.05% to about 10% by weight; in another embodiment,the concentration of HF is between about 1% by weight to about 6% byweight; in another embodiment, the concentration of HF is between about2% by weight to about 4% by weight; in another embodiment, theconcentration of HF is about 3%; in another embodiment, theconcentration of HF is greater than 0% to less than about 5% by weight.The amount of HF added is sufficient to form a mixture, which canseparate out the 244bb and to form a product which is substantially freeof 1233xf and which is purer in the 244bb than the resulting mixture. Inan embodiment, the resulting mixture is not a ternary azeotrope orternary azeotropic-like composition. In another embodiment, theresulting mixture forms a ternary azeotrope or ternary azeotropic-likecomposition. The amount of HF present in the mixture is less than about10 wt % of the mixture. In another embodiment, HF is present in lessthan about 5 wt % of the mixture. In still further embodiment, theamount of HF is present is less than about 3 wt % of the mixture. Theresulting composition is distilled and the product substantially free of1233xf is collected from the column reboiler and is fed forward to Step(3) reactor. A stream consisting of mainly 244bb/1233xf/HF exits the topof the column and is recycled back to the phase separator.

In Step (3) of the subject process to produce 1234yf, the 244bb is fedto a second vapor phase reactor (dehydrochlorination reactor) to bedehydrochlorinated to make the desired product2,3,3,3-tetrafluoroprop-1-ene (1234yf). This reactor contains a catalystthat can catalytically dehydrochlorinate HCFC-244bb to make HFO-1234yf.

The catalysts may be metal halides, halogenated metal oxides, neutral(or zero oxidation state) metal or metal alloy, or activated carbon inbulk or supported form. Metal halide or metal oxide catalysts mayinclude, but are not limited to, mono-, bi-, and tri-valent metalhalides, oxides and their mixtures/combinations, and more preferablymono-, and bi-valent metal halides and their mixtures/combinations.Component metals include, but are not limited to, Cr³⁺, Fe³⁺, Mg²⁺,Ca²⁺, Ni²⁺, Zn²⁺, Pd²⁺, Li⁺, Na⁺, K⁺, and Cs⁺. Component halogensinclude, but are not limited to, F⁻, Cl⁻, Br⁻, and I⁻. Examples ofuseful mono- or bi-valent metal halide include, but are not limited to,LiF, NaF, KF, CsF, MgF₂, CaF₂, LiCl, NaCl, KCl, and CsCl. Halogenationtreatments can include any of those known in the prior art, particularlythose that employ HF, F₂, HCl, Cl₂, HBr, Br₂, HI, and I₂ as thehalogenation source.

When neutral, i.e., zero valent, metals, metal alloys and their mixturesare used. Useful metals include, but are not limited to, Pd, Pt, Rh, Fe,Co, Ni, Cu, Mo, Cr, Mn, and combinations of the foregoing as alloys ormixtures. The catalyst may be supported or unsupported. Useful examplesof metal alloys include, but are not limited to, SS 316, Monel 400,Inconel 825, Inconel 600, and Inconel 625. Such catalysts may beprovided as discrete supported or unsupported elements and/or as part ofthe reactor and/or the reactor walls.

Preferred, but non-limiting, catalysts include activated carbon,stainless steel (e.g. SS 316), austenitic nickel-based alloys (e.g.Inconel 625), nickel, fluorinated 10% CsCl/MgO, and 10% CsCl/MgF₂. Thereaction temperature is preferably about 300-550° C. and the reactionpressure may be between about 0-150 psig. The reactor effluent may befed to a caustic scrubber or to a distillation column to remove theby-product of HCl to produce an acid-free organic product which,optionally, may undergo further purification using one or anycombination of purification techniques that are known in the art.

The following examples of the invention are not to be construed aslimiting.

Example 1

This example illustrates the addition of HF into a mixture of 244bb,1233xf, 1232zf, 243 isomer, and 1230xa dimers in separating 1233xf andother recyclable by-products in subsequent distillation. Thedistillation column used consisted of a 10 gallon reboiler, 2 inch ID by8 feet Propack column, and a 5 ft² shell and tube condenser. The columnis packed with Monel ¼″ Pro-Pack dump packing and has about 30theoretical plates. The distillation column is equipped withtemperature, pressure, and differential pressure transmitters.

59.7 lbs of a mixture containing HF, 1233xf, 1232xf, 243, and some heavycomponents (boiling point higher than ˜0.60° C.) are charged to thedistillation column with 10 gallon reboiler. The mixture consists of 95%HF and 5% organic as indicated above. The column is brought into a totalreflux. Temperature of the reboiler is ˜36° C. and the column pressureis ˜13 psig. The sample is then taken from the column overhead. Thesample contains some HF as verified by pH measurement. The GC analysisof organic portion reveals 1.1% 244bb, 76.8% 1233xf, 3.4% 243, 13.9%1232xf, and 4.8% of other compounds.

Example 2

This example illustrates how the addition of HF into a mixture of 244bband 1233xf helps remove 1233xf in subsequent distillation. Thedistillation column used consisted of a 10 gallon reboiler, 2 inch ID by8 feet Propack column, and a 5 ft² shell and tube condenser. The columnwas packed with Monel ¼″ Pro-Pack dump packing and had about 30-35theoretical plates. The distillation column was equipped withtemperature, pressure, and differential pressure transmitters.

106 lbs of 3% HF/92.15%244bb/4.85%1233xf was charged into reboiler.Batch distillation was started at 40 psig. Samples were periodicallytaken from column overhead and reboiler and analyzed by GC for organiccompositions and by acid-base titration for HF concentrations.Continuous distillation was initiated after 244bb concentration in thereboiler reached about 98 GC area % (or 1233xf was about 2 GC area %).The mixed feed comprising HF, 244bb, and 1233xf was continuously fedinto column as a liquid form through a feeding port located in themiddle of the column. The overhead stream was directed to a 10 wt % KOHaqueous solution for acid removal and then the organic was compressedand collected into a PCC (product collection cylinder) after beingpassed through a drying column. The reboiler stream was directlycompressed and collected into another PCC. During the course ofoperation, the liquid level in reboiler was maintained at a constantlevel by keeping the sum of overhead takeoff rate and reboiler removalrate equal to the feed rate. As shown in Table 1, 1233xf was enriched inoverhead stream but depleted in reboiler stream. As a result, 98 GC area% 244bb was obtained from the distillation. Analysis also indicated thatalmost all HF included in feed left distillation column from theoverhead (in other words, no or little HF appeared in reboiler stream).

TABLE 1 Feed OH take- Reboiler Composition at overhead Composition atreboiler Time, rate¹, off rate, stream rate, stream, GC area % stream,GC area % h lb/h lb/h lb/h 245cb 244bb 1233xf others 245cb 244bb 1233xfothers 4 0.5 0.15 0.35 0.0349 92.1626 7.8025 0.0000 8 0.5 0.15 0.350.0102 92.5472 7.4335 0.0091 12 0.5 0.15 0.35 92.5188 7.2292 0.252098.0218 1.9630 0.0152 16 0.5 0.15 0.35 0.0063 91.9291 8.0579 0.0067 200.5 0.15 0.35 0.0075 91.8093 8.1832 0.0000 ¹Feed composition: 3 wt %HF/97 wt % organic (0.0029% 245cb, 94.9636% 244bb, and 5.0335% 1233xf)

Example 3

This distillation was conducted as in Example 2, using in the samedistillation column except that a feed containing only about 400 ppm(about 0.04% by weight) of liquid HF was used. As shown in Table 2, withthe presence of HF at just hundreds of ppm the 1233xf concentrations inthe overhead takeoff stream were above 6 GC area % while they remainedat around 2.5 GC area % in the reboiler drawoff stream, indicating thepresence of HF even at just hundreds of ppm facilitates the separationof 1233xf from 244bb.

TABLE 2 Feed OH take- Reboiler Composition at overhead Composition atreboiler rate, off rate, stream rate, stream, GC area % stream, GC area% Time, lb/h lb/h lb/h 245cb 244bb 1233xf others 245cb 244bb 1233xfothers 4 1.5 0.9 0.6 93.6515 6.3485 0.0000 97.5396 2.4604 0.0000 8 1.50.9 0.6 93.6585 6.2925 0.0490 97.5003 2.4997 0.0000 12 1.5 0.9 0.694.2539 5.7461 0.0000 16 1.5 0.9 0.6 93.9344 6.0656 0.0000 20 1.5 0.90.6 93.7662 6.2338 0.0000 97.4410 2.5434 0.0156 24 1.5 0.9 0.6 93.89836.1017 0.0000 97.4466 2.5534 0.0000 28 1.5 0.9 0.6 93.7186 6.2814 0.000097.4543 2.5457 0.0000 32 1.5 0.9 0.6 93.8642 6.1358 0.0000 97.42302.5770 0.0000 36 1.5 0.9 0.6 93.8747 6.1253 0.0000 40 1.5 0.9 0.693.6065 6.3935 0.0000 44 1.5 0.9 0.6 93.7067 6.2933 0.0000 97.41512.5849 0.0000 48 1.5 0.9 0.6 93.7888 6.2112 0.0000 97.3860 2.614 0.000052 1.5 0.9 0.6 93.8067 6.1933 0.0000 56 1.5 0.9 0.6 93.6921 6.30410.0038 60 1.5 0.9 0.6 93.7278 6.2722 0.0000 97.3845 2.6155 0.0000 ¹Feedcomposition: ~400 ppm HF/~99.96 wt % organic (94.9376% 244bb, and5.0554% 1233xf)

1.-6. (canceled)
 7. A process to prepare 2-chloro-3,3,3-trifluoropropene(1233xf) comprising providing a starting composition comprising at leastone starting compound of formula I, II and/or formula IIICX₂═CCl—CH₂X  (I)CX₃—CCl═CH₂  (II)CX₃—CHCl—CH₂X  (III) wherein X is independently selected from F, Cl, Br,and I, provided that at least one X is not fluorine; (a) contacting saidstarting composition with a fluorinating agent under conditionseffective to produce a first composition comprising 1233xf, unreactedfluorinating agent, HCl, optionally unreacted starting compound, and oneor more organics selected from the group consisting oftrichlorofluoropropene (1231) isomers, 2,3-dichloro-3,3-difluoropropene(1232xf), 2-chloro-1,1,1,2-tetrafluoropropane (244bb),1,1,1,2,2-pentafluoropropane (245cb), dichlorotrifluoropropane (243),trichlorodifluorpropane (242), and one or more dimers selected from thegroup consisting of C₆H₃F₆CI, C₆H₃F₇Cl₂, C₆F₆Cl₂, C₆H₈Cl₂, C₆F₅Cl₃,C₆H₃F₂Cl₅, and combinations thereof; (b) separating, from the firstcomposition, a second composition comprised of an amount of 1233xf andsubstantially all of said organics and dimers; (c) adding HF to thesecond composition in an amount effective to form a third compositioncomprising HF-azeotropes of 1233xf and at least one of the organics,said second composition further comprising the dimers; (d) separatingthe HF-azeotropes from the third composition; and (e) recovering 1233xffrom the HF-azeotopes of separated in step (d).
 8. The process of claim7 wherein the separation of step (b) is by phase separation.
 9. Theprocess of claim 7 wherein the separation of step (d) is bydistillation.
 10. A process to prepare 2,3,3,3-tetrafluoropropene(1234yf) comprising: a) providing a first intermediate compositioncomprising 2-chloro-3,3,3-trifluoropropene (1233xf) as preparedaccording to claim 7; b) contacting said first intermediate compositioncomprising 1233xf with a first concentration of HF in the presence of afluorination catalyst under conditions effective to produce a secondintermediate composition comprising 244bb; and c) dehydrochlorinating atleast a portion of said 244bb to produce a reaction product comprising1234yf.
 11. The process of claim 10 wherein the second intermediatecomposition further comprises unreacted 1233xf.
 12. The process of claim10 wherein a second concentration of HF is added to the secondintermediate composition to in an amount effective to from an azeotropewith the unreacted 1233xf.
 13. The process of claim 12 wherein theazeotrope of the unreacted 1233xf is separated from the 244bb.
 14. Theprocess of claim 13 wherein the azeotrope of the unreacted 1233xf isseparated from the 244bb by distillation.
 15. The process of claim 13wherein the unreacted 1233xf is recovered.
 16. The process of claim 15wherein the unreacted 1233xf is recycled to step (a).
 17. The process ofclaim 12 wherein the HF is added in an amount of between about 0.01% toabout 20% based on the weight of the second intermediate composition.18. The process of claim 17 wherein the HF is added in an amount ofbetween about 0.05% to about 10%. 19.-20. (canceled)